#define _CRT_SECURE_NO_WARNINGS 1
#include<bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1e5 + 10;
ll a[N], prefix[N];

bool cmp(ll x, ll y) {
    return x > y;
}

int main() {
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int n; cin >> n;
    for (int i = 1; i <= n; i++) cin >> a[i];
    sort(a + 1, a + n + 1, cmp);
    for (int i = 1; i <= n; i++) prefix[i] = prefix[i - 1] + a[i];
    ll ans = 0;
    for (int i = 1; i <= n; i++) {
        if (i % 2 == 0) ans = max(ans, prefix[i]);
    }
    cout << ans << '\n';
    return 0;
}